每种语言都有自己的运算符，php，javascript，mysql等下面介绍mysql运算符
Mysql可以通过运算符来对表中数据进行运算，比如通过出生日期求年龄等

运算符包括四类，分别是：算数运算符、比较运算符、逻辑运算符和位运算符

算数运算符
加、减、乘运算

代码如下:

mysql> select a,a+5,a*2 from t1;

+------+------+------+

| a    | a+5  | a*2  |

+------+------+------+

|   24 |   29 |   48 |

+------+------+------+

 row in set (0.00 sec)


这里的原值为24,后面也可以使用混合运算，只需要注意优先级即可

除法和取模运算

代码如下:

mysql> select a,a/3,a div 3,a%5,mod(a,5) from t1;

+------+--------+---------+------+----------+

| a    | a/3    | a div 3 | a%5  | mod(a,5) |

+------+--------+---------+------+----------+

|   24 | 8.0000 |       8 |    4 |        4 |

+------+--------+---------+------+----------+

 row in set (0.00 sec)


此处 / 和 div 代表整除，% 和 mod 代表取模

要注意的是，如果被除数为0,那么计算结果是NULL

比较运算符
数值比较

代码如下:

mysql> select a,a=24,a<12,a>40,a>=24,a<=24,a!=24,a<>24,a<=>24 from t1;

+------+------+------+------+-------+-------+-------+-------+--------+

| a    | a=24 | a<12 | a>40 | a>=24 | a<=24 | a!=24 | a<>24 | a<=>24 |

+------+------+------+------+-------+-------+-------+-------+--------+

|   24 |    1 |    0 |    0 |     1 |     1 |     0 |     0 |      1 |

+------+------+------+------+-------+-------+-------+-------+--------+

 row in set (0.00 sec)


这里的1代表真，0代表假，需要说明的是<>和<=>

<>代表不等于，等同于!=

<=>代表等于，等同于=

此外，等于和不等于不仅可以比较数值，还能比较字符串

字符串比较

代码如下:

mysql> select a,a='24','ha'<>'ha','xa'='xa','b'!='b' from t1;

+------+--------+------------+-----------+----------+

| a    | a='24' | 'ha'<>'ha' | 'xa'='xa' | 'b'!='b' |

+------+--------+------------+-----------+----------+

|   24 |      1 |          0 |         1 |        0 |

+------+--------+------------+-----------+----------+

 row in set (0.00 sec)

is null 和is not null

代码如下:

mysql> select a,a is null, a is not null from t1;

+------+-----------+---------------+

| a    | a is null | a is not null |

+------+-----------+---------------+

|   24 |         0 |             1 |

+------+-----------+---------------+

 row in set (0.00 sec)


这里可以判断是否为空，NULL也可以跟NULL比较

between and和not between and

代码如下:

mysql> select a,a between 15 and 30,a not between 15 and 30 from t1;

+------+---------------------+-------------------------+

| a    | a between 15 and 30 | a not between 15 and 30 |

+------+---------------------+-------------------------+

|   24 |                   1 |                       0 |

+------+---------------------+-------------------------+

 row in set (0.00 sec)


between and 和not between and可以判断数值是否在某一区间内